Diabetes is one of the most serious health issues facing humanity with The World Health Organization reporting that approximately 346 million people worldwide have already been diagnosed with diabetes, making it a global challenge. Diabetes is a chronic disease that manifests when insulin production by the beta cells of the pancreas is insufficient. Among type 2 diabetes patients, there is a 50-80% reduction in beta cell mass by the time of diagnosis compared to a reduction in beta mass by 90% or more among type 1 patients, who commonly have an autoimmune component to their beta cell loss. Two recent NIH studies, one in children and adolescents and the other in adults demonstrate that intensive lifestyle interventions designed to improve and impact diabetes simply have no effect in children and adolescents and cannot be sustained over time among adults.
The TODAY Study Group. N Engl J Med. 2012 Apr. 29. [Epub ahead of print]. Diabetes Research Program Prevention Group, Lancet. 2009; 374(9702): 1677-1686. Among children and adolescents with type 2 diabetes, therapy with metformin or lifestyle interventions did not improve diabetes control or the necessity to go the insulin therapy. The TODAY study illustrates the need for new insulin-secreting beta cells to delay or prevent the adverse vascular complications of diabetes. Despite the many new treatment and technological armamentariums for diabetes, the diabetes-related complications including retinopathy, blindness, neuropathy, amputations, renal insufficiency and dialysis, along with the macrovascular complications including heart attack, stroke and peripheral vascular disease have risen among patients with diabetes. For example, recent studies among patients with type 1 utilizing advances including the use of glucose sensors and insulin pumps did not improve hemoglobin A1C levels as much as those seen in the DCCT trial conducted more two decades ago when there were much more limited treatment options. The DCCT Research Group. N Engl J Med. 1993; 329(14):977-986, Bergenstal R M et al, N Engl J Med, 2010; 363(4):311-320. Bergenstal R M, et al, Diabetes Care. 2011; 34(11):2403-2405.
There is a dire need to restore new beta cells and maintain beta cell mass among type 1 and type 2 diabetes. The loss of endogenous insulin is directly correlated with a multiplicity of atherogenic risk factors for microvascular and macrovascular complications. Lack of insulin, which is the a hallmark of diabetes results not only in elevated glucose levels, but also results in a large number and wide complexity of metabolic abnormalities. For example, lack of insulin results in diminished activation of lipoprotein lipase resulting in increased levels of triglyceride-rich lipoproteins including chylornicrons and very low-density lipoproteins.
The leading hypothesis of how new beta cells can be formed in both children and adults is based upon the original works of scientists nearly a century ago who identified that in acute pancreatic injury there is new beta cell growth. Frederick Banting, discovered insulin in 1921, by clamping the pancreatic ducts to induce the formation of new pancreatic cells. Dr. Banting collected the pancreatic secretions after acute pancreatic ligation and these secretions became known as insulin. Banting F G and Best C H. J Lab Clin Med. 1922; 7:464-472. This work was supported by several earlier scientists, who described that although the population of beta cells is primarily formed during embryogenesis, there is the ability to grow new beta cells postnatally, through a process of transformation of ductal cell tissue into insulin-producing tissue. By 1920, the regenerative powers of the pancreas were well described. Frederick Banting attributes his studies leading to the discovery of insulin on the work of Moses Barron who documented that regeneration of injured pancreatic tissue manifests from the pancreatic ducts. Barron M. Surg Gynec Obstet. 1920; 19:437-448. Prior to the widespread availability of insulin, surgeons performed partial pancreatectomies on diabetic children in the hopes of stimulating beta cell regeneration. DeTakats G. Endocrinology. 1930; 14:255-264. Benefits from these novel procedures were described, but were short-lived, likely because of ongoing autoimmune destruction.
The ability to generate fully-functional pancreatic beta cells, through the differentiation of non-endocrine cells has now been shown by more than a dozen research groups including The Section of Islet Cell and Regenerative Biology at Joslin Diabetes Center at Harvard University and The Departments of Beta Cell Regeneration at the Hagedorn Research Institute in Denmark.
Over the past several decades, the regenerating gene (Reg or REG) family has emerged among many species, including humans, as a key initiating factor in the process of beta regeneration from nonendocrine tissue within the pancreas. Levetan C., 2010, J Diabetes; 2(2):76-84. The Reg genes are associated with beta regeneration and are upregulated in the pancreas during embryogenesis when the pancreas is being populated with beta cells for the first time. After fetal development when the pancreas is populated with endocrine cells for the first time, the Reg genes are usually undetectable, but are upregulated in response to acute pancreatic injury including pancreatic stones, pancreatitis, pancreatic duct ligation and wrapping, partial pancreatectomy and pregnancy.
It is also known from the Human Genome Project that there are many genes that are responsible for making cells of the different organs and populating organs for the first time (such as the brain, heart, kidney and pancreas) and such genes are expressed almost exclusively during embryological development. The regenerating gene family of proteins (Reg) are expressed almost exclusively during embryological development and then only expressed when there is acute pancreatic injury as a mechanism to help repair the injured organ. Typically in both type 1 and 2 diabetes, the rate of tissue demise exceeds the rate of regeneration despite Reg gene upregulation. To date, 17 Reg family genes have been identified. Identified members of the human REG gene family (REG) include Regenerating islet-derived 1 alpha (REG1α or REG1a), REG1β, also known as REG 1b, REG 3α, also known as REG 3a, REG 3β, also known as REG 3b and REG 4.
This invention identifies and confirms peptide sequences that are highly conserved and 100% identical within the human Reg 1a, human Reg1b, human Reg3a and human Reg 4 proteins and identical Reg peptide sequences within four other mammalian species. This inventor has previously described the role of a 14-amino acid Human Reg3a peptide in pancreatic islet development. This present invention, identifies peptide sequences contained within the human Reg1a, Reg1b, Reg3a and Reg4 that are not contained within the previously described, prior art human 14-amino acid peptide Reg3a protein and the 15-amino acid hamster Reg3gamma protein, resulting in beta cell regeneration. The Reg peptides described within this invention, bind directly to the Reg Receptor on pancreatic extra-islet ductal tissue. In contrast to the earlier study of the 14-amino acid peptide, which is shown to (Levetan C S et al, Endocr Pract. 2008; 14(9):1075-1083) interact with the Reg receptor but does not directly bind to it.
This invention also specifically identifies a binding region within human Reg Receptor and the bioactive peptides within the Reg gene protein that bind directly to the Reg Receptor that are not included in the prior art of the 15-amino acid hamster Reg3gamma sequence known as Islet Neogenesis Associated Protein/INGAP or the 14-amino acid human Reg3a peptide known as Human Proislet Peptide/HIP. This invention demonstrates the utility of these peptides, derivatives, peptidomimetics and stimulatory antibodies that have been generated from the specific binding regions of the Reg Receptor for the generation of new human beta cells
Kapur, Watanabe, Zenilman and others have provided evidence that Reg peptides play a direct role in stimulating beta cell formation from non-endocrine pancreatic tissue. Kapur R et al Islets. 2012; 4(1), Watanabe T et al Proc Natl Acad Sci USA. 1994, 26; 91(9):3589-92. Zenilman M E, et al Pancreas. 1998; 17:256-261. The previously described human 14-amino acid peptide (Human Proislet Peptide) and 15-amino acid peptide (hamster) (Islet Neogenesis Associated Protein/INGAP) from the human and hamster Reg3 gene protein have demonstrated the ability to not only restore normoglycemia via restoration of new beta cells in animal models, but also to generate new beta cells in humans via the transformation of extra-islet ductal tissue into new endocrine cells including demonstrating the formation of new beta cells from human pancreatic ductal tissue. Levetan C S et al, Endocr Pract. 2008; 14(9):1075-1083, Rosenberg L et al, Diabetologia. 1996; 39:256-262, Li J et al, Peptides. 2009; 30(12):2242-2249, Dungan K M et al, Diabetes Metab Res Rev. 2009; 25(6):558-565.
Previously, this inventor demonstrated that a human Reg3a gene protein has successfully been administered to human pancreatic ductal tissue devoid of islets resulted in a significant increase in insulin concentrations indicating new beta cell formation resulted a 3-fold rise in total beta cells staining insulin in STZ-rendered diabetic mice. Levetan C S., et al, Endocr Pract. 2008; 14(9):1075-1083. Reg3a protein and placebo-treated mice underwent an overnight fast and a fasting glucose level on the morning of day 39 of treatment. Fasting glucose levels were 258.00±84.5 mg/dl in the placebo group compared a fasting glucose 111.00±11.4 mg/dL (P=0.020) in the Reg3a protein treated mice.
Two studies by separate investigators have shown the ability of Reg peptide to transform human extra-islet pancreatic exocrine tissue into new beta cells, in vitro. These studies were conducted by a methodology utilized in pancreatic islet transplantation, in which the pancreatic endocrine beta cells are separated from the exocrine ductal tissue and the exocrine ductal tissue are shown to transform into new beta cells in the presence of Reg peptide. Li J, et al. Peptides 2009; 30:2242-9, Assouline-Thomas B G, Diabetes 2008, 57(Suppl; 1) A2413. Using the current gold-standard (BrdU labeling), which distinguishes whether new beta cells are formed by the budding from pre-existing beta cells versus being formed from extra-islet ductal exocrine tissue were conducted in rodents using BrdU labeling of the beta cell lineage, which can distinguish whether new beta cells are being derived from replicating beta cells versus beta cells being formed from non-endocrine, extra-islet pancreatic exocrine tissue. Kapur R, et al, Islets. 2012; 4(1).
The Section of Islet Cell and Regenerative Biology at Joslin Diabetes Center found that the 15-amino acid hamster INGAP Reg3 gamma peptide was present in the newest beta cells and islets that were formed directly from branching proliferating extra-islet ducts, which also confirms that mechanism of action of Reg peptide is to form new beta cells from extra-islet exocrine tissue. Guo L et al, Diabetes. 2010, 59(suppl; 1) A2589. When Reg is inhibited by the administration of a blocking antibody in an animal model of pancreatic injury, there was attenuated recovery, also confirming that Reg's role is both protective and regenerative during acute pancreatic injury. Viterbo D, et al. JOP. 2009; 10(1):15-23.
The Departments of Beta Cell Regeneration at the Hagedorn Research Institute and Peptide and Protein Chemistry at Novo Nordisk reported a 2-fold increase in the volume of new small islets developing from non-endocrine tissue resulting from the treatment with both the human 14 amino acid Reg3a peptide, HIP, and the 15-amino acid Reg3gamma hamster peptide, INGAP. Kapur R, et al, Islets. 2012; 4(1):Epub. Five days after treatment with both the 14-amino acid human Reg3a peptides, HIP, and the 15-amino acid hamster Reg3gamma peptide, INGAP, there were increased levels of new islet markers necessary for islet formation, including NGN3, NKX6.1, SOX9, and INS, indicating that REG is a catalyst for beta cell neogenesis. Kapur R, et al, Islets. 2012; 4(1). Similar to these findings, other data support that the Reg protein is an initiating factor to downstream regulation of new beta cells. Levetan C., 2010, J Diabetes; 2(2):76-84. For example, when Reg is initially expressed, PDX-1, PAX1, Ngn3, Nkx6.1, Sox9 and Ins, are not expressed, and once Reg is present, PDX-1, PAX1, Ngn3, Nkx6.1, Sox9 and Ins and other beta cell proliferation factors become present demonstrating that Reg activates downstream factors necessary for beta cell regeneration. Vukkadapu S S Physiol Genomics 2005:21, 201-211, Kapur R., et al., Islets. 2012; 4(1):Epub. Gun and colleagues confirmed positive Reg staining in ductal epithelium in acutely diabetic NOD mice and in the pancreas of a type 1 healthy cadaveric human pancreata or in healthy mice.
The organ specificity of Reg proteins to the pancreatic ducts has been illustrated by tagged Reg protein labeled with fluorescein isothiocyanate that was administered via intraperitoneal injection to rodents. The only organ that had fluorescent staining was the pancreas with labeling only found specifically to be within the nonendocrine pancreatic ductal populations, again confirming that the mechanism of action of Reg is transformation of extra-islet ductal cells into beta cells. Pittenger G L et al, Diabetologia 2009; 52 (5):735-738. There are now numerous studies confirming that the mechanism of action of the Reg peptides is to transform extra-islet exocrine ductal tissue into new islets rather than the newly formed beta cells resulting from the budding of existing beta cells.
Both the 14-amino acid Reg3a peptide, HIP, and 15-amino acid Reg3gamma peptide, INGAP, are currently in human clinical trials. Human clinical trials with the 15-amino acid hamster peptide have already resulted in an increase in stimulated C-peptide by 27% (p=0.0057) in type 1 patients. Dungan K M et al, Diabetes Metab Res Rev. 2009; 25(6):558-565.
The REG genes encode proteins secreted by the exocrine pancreas, which has been associated with beta cell regeneration in rodents. Terazono K., et al., J Biol Chem (1988), 263: 2111-2114. REG1a, REG1b, REG3a and REG4 belong to the C-lectin family and are randomly clustered on 2p12. They share structural and some functional properties and encode proteins that are members of the Reg family with sequence homology as described in this invention. Their products are secretory proteins of the C-type lectin superfamily that are involved in beta cell regeneration and proliferation.
Specifically for type 1 diabetes, this invention describes a novel approach for the reversal of the disease by administering an immune tolerance agent prior to the initiation of Reg peptides described in this invention. To date, more than 100 different immune agents have been administered to type 1 diabetes rodent models, as well as to human subjects with new onset type 1 diabetes. Although many have been successful in the reversal of diabetes in rodents, none have successfully reversed diabetes in man and led to insulin independence. There have been several agents demonstrating promise in terms of immune blockade, but beta regeneration is too slow to render patients insulin-free despite the blocked immune attack on beta cells. This invention combines the administering of an immune tolerance agent prior to the administration of the Reg peptide for beta regeneration in order to accelerate the regeneration process for successful reversal of diabetes.
Both the sequences and the 3-Dimensional Structures of the human Reg gene proteins are very similar in that each has a similar binding arm that protrudes from the main structure that is the binding region for the Reg Receptor. Human Reg1a contains 166 amino acids. Human Reg1b contains amino 166 acids. Human Reg3a contains 174 amino acids. Human Reg4 contains 158 amino acids.
This invention identifies peptide sequences that are within the human Reg1a, human Reg1b, human Reg3a and human Reg4 proteins that have not been previously described for the usage of beta cell generation. This invention specifically demonstrates that homologous peptides within the human Reg1a, human Reg1b, human Reg3a and Reg4 gene protein bind directly to the human Reg receptor, which results in the acceleration of the generation of new beta cells from pancreatic ductal tissue. Although both the 15-amino acid hamster sequence (Islet Neogenesis Associated Protein/INGAP) and 14-amino acid human Reg3a peptide (Human Proislet Peptide) act through the Reg receptor to generate new beta cells, neither of these peptides directly binds directly to the human Reg receptor, which is confirmed in this invention. Also identified is a bioactive domain within the Reg receptor that is immunogenic and stimulatory antibodies to this binding site have been generated.
A putative Reg Receptor initially described in rodents, was found by this inventor to be present in human pancreatic ductal tissue. The prior art described that the 14-amino acid human Reg3a peptide (HIP) interacted with the human Reg Receptor resulting in downstream signaling and generation of new beta cell formation. Levetan C S., et al, Endocr Pract. 2008; 14(9):1075-1083. This present invention demonstrates that the 7-9 amino acid human Reg peptides bind directly to the Reg Receptor and are not contained within the prior art, 14-amino acid human Reg 3a peptide or the 15-amino acid hamster Reg3gamma peptide.
The Reg Receptor and has been described and known as hereditary Multiple Exostoses Gene Isolog with other names describing this receptor including REG RECEPTOR, Reg Receptor, BOTV, BOTY, DKFZp686C2342, exostoses (multiple)-like 3, Exostosin-like 3, EXT-related protein 1, EXTL1, HHREG RECEPTOR, EXTR1, EXTL3 Glucuronyl-galactosyl-proteoglycan-4-alpha-N-acetylglucosaminyltransferase, KIAA0519, Multiple exostosis-like protein 3, REGR and RPR. exostoses (multiple-like 3, Glucuronyl-galactosyl-proteoglycan, 4-alpha-N-acetylglucosaminyltransferase, exostosin-like3, Hereditary multiple exostoses gene isolog, reg receptor, Multiple exostosis-like protein 3, and EC2.4.1).
The receptor was named for its similarities to the Exostoses family of genes by homology screening, but it was specifically noted that this receptor is not derived from the Exostoses (EXT and EXTL) genes. Rather, the Reg Receptor protein (FIG. 4) was categorized as a member of the Exostosin family because it demonstrates a 52% homology to the 262 amino acid C-terminal of the Exostosin-like 2 protein and a 40% homology with the 242 amino acid C-terminal of the Exostosin-like 1 protein, yet there is no homology of Reg Receptor to the N-terminal regions of Exostosin-1 or 2. Kobayashi S. et al., Anat. Embryol. 207:11-15, 2003. Reg Receptor was initially isolated and described by Van Hul and colleagues in 1998 as a 919 amino acid protein Reg receptor contains a 23 amino acid unique N-terminal region containing a transmembrane domain (residues 28-51) and a short intracellular region at the N terminus. Reg Receptor is located on chromosome 8p21. Saito T. et al, Biochem Biophys Res Commun. 1988, 242(1):61-66, Van Hul W et al., Genomics. 1998; 47(2):230-7.
The N-terminal region (residues 1-656) of the Reg Receptor has no homology to any other members of this family of genes. The 1.6-kbp cDNA, which was initially isolated in the screening of the rat islet cDNA expression library as a Reg-binding protein, contained the N-terminal region alone (amino acid residues 1-332). Kobayashi S. et al., Anat. Embryol. 207:11-15, 2003. Because no other members of the EXT family bind to Reg proteins, the Reg binding domain is shown in this invention within the N-terminal region of Reg Receptor.
While it has been recognized that is a putative Reg Receptor in rodents, this invention is the first to demonstrate peptides not contained within the human 14-amino acid Reg3a, and contained within the human Reg1a, Reg1b, Reg3a and Reg4 protein and bind directly to the Reg Receptor leading to new beta cell formation.
Findings by this inventor demonstrate that the Reg Receptor plays a key regulatory role in beta cell growth and generation from extra-islet exocrine tissue inclusive of ducts, acinar cells and progenitor cells contained within these cells. Further, the present invention identifies the binding region within human Reg1a, human Reg1b, human Reg3a and human Reg4 and a binding domain on Reg Receptor, which are targets for the treatment of diabetes and other diseases for which there is need for new beta cells.
The present invention further demonstrates these peptides, which have not been described in the prior art, are unique Reg peptides for binding to the Reg Receptor on the surface pancreatic ductal tissue and are pivotal for new beta cell formation either via direct usage of the peptide, derivatives, optimized versions, peptidomimetics that bind to Reg Receptor or via stimulating antibodies generated from unique binding sites within the Reg Receptor that generate new beta cells.
This invention finds the Reg Receptor to be a pivotal receptor and a specific site within the Reg Receptor to be the site of Reg binding resulting in the translocation of the Reg Receptor through the cytoplasm to the nucleus of extra-islet exocrine tissue inclusive of ducts, acinar cells and progenitor cells contained within these cells, generating beta cell growth, acceleration and turnover.